Therapeutic benefits can be realized by administering an active agent to a subject over an extended period of time. To this end, controlled-release drug delivery systems have been developed to control the rate of drug delivery to the subject. Controlled-release drug delivery systems can include both delayed release and sustained release systems.
Site-specific drug delivery can also offer therapeutic benefits. Site-specific drug delivery refers to the delivery of an active agent to a specific target tissue site, instead of systemically. Site-specific drug delivery offers advantages because the effect of the active agent on the target tissue can be enhanced while side effects of the active agent on other tissues can be reduced.
One technique for providing controlled-release site-specific drug delivery is to use a drug-eluting coating system disposed on a medical device. The coating can serve to control the rate at which the active agent is eluted while the fact that the coating is disposed on a medical device allows delivery of the active agent to be site-specific. As an example of this approach in use, stents with drug-eluting coatings are routinely inserted into patients to prevent restenosis of the stented artery.
In some cases it can be desirable to dispose a coating only on certain portions of a medical device. For example, in some contexts, it can be desirable to dispose a coating primarily on the abluminal (outward facing) surface of a stent. However, this remains technically difficult.